2,6-dimethylheptan-4-one

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes

Specific details on test material used for the study:

- Name of test material: 85% w/w 2,6-dimethyl-4-heptanone and 15% w/w 4,6-dimethyl-2-heptanone
(Diisobutyl Ketone)
- Physical state: transparent colorless liquid
- Analytical purity: 91.4%
- Lot/batch No.: SL3055T643

Analytical monitoring:

yes

Details on sampling:

- Sampled on: day 0, 1 and 2

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A stock solution of 200 mg/L was prepared by adding 542 µL DIBK to 2 L of Adjusted Laboratory Dilution Water (ALDW)
- Controls: ALDW without test substance

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Source: In-house cultures initially obtained from New England Bioassay, Inc., Manchester, Connecticut
- Age at study initiation (mean and range, SD): < 24h

Test type:

semi-static

Water media type:

freshwater

Total exposure duration:

48 h

Hardness:

148 - 156 mg CaCO3/L

Test temperature:

19 - 21°C

pH:

7.5 - 7.7

Dissolved oxygen:

7.7 - 8.7 mg/L

Nominal and measured concentrations:

Nominal concentrations: control, 4.67 - 7.78 - 13.0 - 21.6 - 36.0 - 60.0 mg/L
Measured concentrations: less than quantification limit of 0.911 mg/L (control) - 3.15 - 5.53 - 9.66 - 15.9 - 26.6 - 55.6 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass serum bottles
- Type: closed (sealed with an aluminium seal, containing a Teflon-lined rubber septa)
- Material, fill volume: glass, approx. 160 mL of total volume (void of headspace)
- Renewal rate of test solution: on day 1
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Obtained from the upper Saginaw Bay of Lake Huron off Whitestone Point. Before use in the laboratory, the water was sand-filtered, pH-adjusted with gaseous CO2, carbon-filtered, and UV-irradiated. The daphnid water was prepared by adjusting laboratory water to a hardness of about 170 mg/L as CaCO3 before autoclaving. Afterwards the water was autoclaved at 121°C and 18 psi for 30 min, cooled and aerated for approx. 24h.
- Total organic carbon: 1040 µg/L
- Pesticides: below detection limit
- Intervals of water quality measurement: weekly


OTHER TEST CONDITIONS
- Photoperiod: 16:8 hours
- Light intensity: 2050 +/- 350 lux


EFFECT PARAMETERS MEASURED: immobility


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.66
- Range finding study
- Test concentrations: control - 2.50 - 5.00 - 25.0 - 50.0 - 250 - 500 mg/L
- Results used to determine the conditions for the definitive study: 100% immobility at test concentrations of 500 - 250 - 50 mg/L; 20% immobility at test concentrations of 5.00 mg/L; no immobility was observed in the remaining test concentrations.

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

55.6 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

37.2 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 31.3 - 45.2 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

15.9 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Reported statistics and error estimates:

An appropriate U.S. EPA computer program was used to calculate the 24- and 48h EC50 values and corresponding 95% confidence intervals. The Probit Program and the Trimmed Spearman-Karber (TSK) Program were available.

The test exhibited a 48h EC50 of 37.2 mg/L and a 48h NOEC of 15.9 mg/L. The test concentrations are based on the mean measured concentrations because the measured test concentrations in the test vessels ranged from 59.4 - 92.3% (day 0), 55.0 - 93.7% (day 1), 73.9 - 89.7% (day 2). The lower percent of target concentrations were likely due to the volatility of the test substance.

Validity criteria fulfilled:

yes

Executive summary:

The acute toxicity of 2,6 -dimethylheptan-4 -one (diisobutyl ketone or DIBK) to the cladoceran, Daphnia magna, was evaluated following OECD guidelines (OECD 202) over a 48-hour exposure period. These data were used to calculate 24 -, and 48 -hour EC50 values and a 48-hour NOEC. The test exhibited a 48h EC50 of 37.2 mg/L and a 48h NOEC of 15.9 mg/L. The test concentrations are based on the mean measured concentrations because the measured test concentrations in the test vessels ranged from 59.4 - 92.3% (day 0), 55.0 - 93.7% (day 1), 73.9 - 89.7% (day 2). The lower percent of target concentrations were likely due to the volatility of the test substance.

Description of key information

A 48-hour static acute test evaluated the toxicity of DIBK to the cladoceran, Daphnia magna.  The test followed OECD 202 and meet GLP

requirements.  The reported 48-hour EC50 value was 37.2  mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

37.2 mg/L

Additional information

Two acute toxicity studies were available for 2,6-dimethylheptan-4-one (also known as diisobutyl ketone or DIBK) exposed to the freshwater cladoceran, Daphnia magna. A 2005 GLP study evaluated the toxicity of DIBK, followed OECD guidelines (OECD 203) and was rated a Klimisch score of 1, therefore it was selected as the Key study. The reported 48-hour EC50 value was 37.2 mg/L. An acute toxicity study, rated a Klimsch score of 2, was included as a supporting study. This supporting study was conducted prior to GLP requirements and followed guidelines outlined in Standard Methods. This supporting study reported a 48-hour EC50 value of 164 mg/L.